Tub sizing of paper



United States Patent TUB sIzINooF PAPER Donald R..Spear and William F.FoWler,zJr., Rochester,

N..Y., assignors to Eastman Kodak Company, Rochester, N. Y., acorporation of New Jersey No Drawing. Appli'cationA-pril-ZZ 1353, SerialNo; 351,472

9 Claims- ((11.117-155) This invention relates to anewprocess of tubsizing paper; More particularly this invention relates totubsizing'photographic paper.

There are two commonly used methods of paper'sizing. According to oneprocedure, called beater or" engine sizing; the-paper chemicals,including those whichgive high dry-bursting strength, and high wetstrength-are added to the=pulp slurry at some point prior to sheet.formation upon the wire of the paper machine proper. In the othermeans'of application,- the dried paper is run through a bath or tubcontaining the sizing material in aqueous solution, dispersion, orsuspension, whereupon the paper'absorbs a quantity of the material. Sucha process is called tub" sizing. Gelatin and starch are often used forthis purpose. The-use of these materials improves variouscharacteristics of highquality raw stock suchas adhesion ofother layerslater applied, freedom from fibers, plus the usually-measured physicalproperties of the. sheet such as mullen and Wet' strength.

Such materials as gelatin are, however, hydrophilic, beingd'eposited inthe interstices of and upon the surface-ofthe'rawstock from a watersolution. They do not; therefore, result in any substantial improvementin tlieresistance to moisture of the paper. We have found that, ifcertain high polymeric aqueous dispersions (here.- inafterreferred to ashydrosols) are used in place of gelatin for tub sizing paper, a markedimprovement results.

An object of this invention is to provide a paper sizing which-reducesthe paper absorbency toward water. Another object of this invention isto provide a paper having'asurface particularly adapted to be. coatedwith a baryta coating in-photographic paper. manufacturing. A furtherobject of this invention is to provide a sizing whichacts'as a binder onpaper which can be applied hysurfacetreatment. An additional'object is.to provide a proeess for coating'paperwith a sizingto form a hard,ablrasive resistant surface.

'Ih'ehydrosols-which'we'use in our. process are disclosed in patentapplication Serial No. 272,709 by William F. Fowler, Jr., filed February20, 1952.

These hydrosolsare' formed-by polymerizing together an unsaturatedaliphatic amide and an acrylate,.preferably with some unsaturatedaromatic monomer therein. Whenput'in the form of an aqueoussolutionand/or dispersion, this mixture can be polymerized by a simple methodwhereby there. results .an emulsioirof thepolymer in a form forimmediate use, such as for mixing with a solution of: gelatin oranyother water-soluble colloid with which-it is to-be.used. Our processinvolves-the 1188:0152

1. An unsaturated aliphatic amide which will be referred=to herein asthe hydrophilic monomer. This compound. will. be. one. having thefollowing structural formula:

Patented May. 29., 1.95.6

where R1 is a hydrogen, halogen, alkyl or cyano v substituent and R2 andR3 may beeither hydrogen or alkyl. I

2. A monomer having the following structural formula:

R4 OH J(I3O -R;-

wherein R6 is hydrogen, halogenlor amalkyl, andRv, Ra, R9, R10 and R11may each be any-of-thefollowing: hydrogen, halogen, alkyl, nitro, cyanoor dialkyl amino.

In compounding the monomers, the monomers designated 1 and 2 should eachbepresentiinia proportionat least 2% of the total monomer composition.However, the sum of these two monomers should constitute atleast 30% ofthe composition. The class of. monomersdesignated 3 should notconstitute any more-than 70%. of the total monomer mixture employed.Although: inv some cases it may be desirable to entirely dispense withthe unsaturated aromatic constituent, it is preferredthat at least 5%thereof, based on the total monomeripresent, be used so as to assure theobtaining ;,of apolymer which is free of tackiness under allconditions-of.operation. As an example of compounds which are useful as.constituent 1, any of the following unsaturated alpihatic amides areuseful for this purpose:

1. Acrylamide 2. a-Ethyl acrylamide u-n-Propyl acrylamide a-Isopropylacrylamide a-n-Butyl acrylamide u-n-OctyI acrylamide N-methyl acrylamideN-ethyl acrylamide N-isopropyl acrylamide 10. N-n-propyl acrylamide 11.N-n-butyl acrylamide 12. N-isobutyl acrylamide"- 13. N-n-hexylacrylamide 14. N,N-dimethyl acrylamide 15. N,N-diethyl acrylamide 16.N,N-di(n-propyl)acrylamide 17. N,N-di(isopropyl)acrylamide 18.N,N-di(n-buty1)acrylamide 19. N,N-di(n-butyl)methacrylamide 20.Methacrylamide Acrylic acid esters: which; are useful as constituent i 2in the? composition; refrredzto: above are the: following:

. Methyl acrylate' Ethyl acrylate n-P'ropyl acrylate Isopropylacrylate'r- 'Isohutylaeryltrte Ioamyl tacryl'ate n=Hexyl acrylate" 9.2-ethyl hexyl acrylate n-Octyl acrylate n-Decyl acrylate Methylmethacrylate Ethyl methacrylate n-Propyl methacrylate Isopropylmethacrylate n-Butyl methacrylate Isobutyl methacrylate n-Amylmethacrylate 2-ethyl hexyl methacrylate n-Octyl methacrylate n-Decylmethacrylate S-Cyanoethyl acrylate B-Cyanoethyl methacrylatefi-Chloroethyl acrylate fi-Chloroethyl methacrylate n-Butyl acrylate Ofthe monomers of the unsaturated aromatic type which may be employed asconstituent 3 where that is used, any compounds selected from thefollowing list may be employed:

1. o-Methyl styrene 2. m-Methyl styrene 3. p-Methyl styrene 4.2,4-dimethyl styrene 5. 2,5-dimethyl styrene 6. 3,4-dimethyl styrene 7.3,5-dimethyl styrene 8. 2,4,5-trimethyl styrene 9. 2,4,6-trimethylstyrene 2,4,5-triethyl styrene o-Ethyl styrene m-Ethyl styrene p-Ethylstyrene 3,5-diethyl styrene p-n-Butyl styrene m-Sec-butyl styrenem-tert-butyl styrene p-hexyl styrene p-n-Heptyl styrene p-Z-ethyl hexylstyrene o-Fluoro styrene m-Fluoro styrene p-Fluoro styrene o-Chlorostyrene m-Chloro styrene p-Chloro styrene 2,3-dichloro styrene2,4-dichloro styrene 2,5-dichloro styrene 2,6-dichloro styrene3,4-dichloro styrene 3,5-dichlor styrene 2,3,4,5,6pentachloro styrenern-Trifluoromethyl styrene o-Cyano styrene m-Cyano styrene m-Nitrostyrene p-Nitro styrene p-Dimethylamino styrene Styrene The preparationof the polymer is carried out by combining the monomers in an aqueoussystem. The amide constituent is soluble in water and the softener orplasticizing monomer, and the unsaturated aromatic compound can beincorporated by dispersing those in water, such as by the use of awetting agent. For this purpose an anionic surface active agent ispreferred, such as sodium lauryl sulfate. Other dispersing agents,however, such as (1) cetyl dimethyl ethyl ammonium bromide, (2) sodiumstearate, (3) sulfonates of an octyl phenoxy polyethylene glycol, (4)sodium salts of alkyl-aryl sulfonates, (5) sodium salts of alkylnaphthyl sulfonates and (6) sodium salts of sulfated monoglycerides maybe employed in this connection. The monomers ordinarily are present in adilute solution, such as within the range of 560%, the monomerconcentration used being not critical but governed by the convenience ofthe individual operator. Also incorporated in the dispersion is acatalyst adapted to promote the polymerization of the monomers. Eitherof two methods of polymerization may be used: (1) heating on a steambath or (2) carrying out at substantially room temperature (IS-30 Q).Where a steam bath polymerization is employed, a water solubleper-compound may be employed as the catalyst, as, for example, ammoniumpersulfate, potassium persulfate, hydrogen peroxide, sodium perborate,sodium peracetic acid or the like. If, on the other hand, thepolymerization 0f the monomer dispersion is carried out at roomtemperature, a redox system catalyst is employed, such as a mixture ofsodium acid sulfite and ammonium persulfate or some other per-compound,a mixture of ascorbic acid and a per-compound or a mixture of a ferrousion compound and a per-compound, or any other redox system catalystwhich has been described as being suitable for promoting thepolymerization of monomers. If the amide component of the dispersion isof the N- substituted type, it is advisable to carry out thepolymerization by the second method, namely, using room temperature anda redox system catalyst. If, on the other hand, the amide employed isnot N-substituted, either carrying out the polymerization at roomtemperature referred to as method 2 or at an elevated temperature, suchas -120 C., as referred to as method 1, may be conveniently employed inpreparing the hydrosol of the polymer in accordance with my invention.It is desirable in carrying out the polymerization that the mass bevigorously agitated, and that the liquid monomer be added over acomparatively short period. For instance, with vigorous agitation andfairly rapid addition of the monomer, products are obtained having ahydrosol particle size on the order of 0.1 micron or less in diameter.On the other hand, if the agitation is not as vigorous or the monomer isadded over a longer period of time, a greater size results. Thepreparation of the polymer should be carried out using sufficient speedof agitation and of addition of monomer, that the size of the particlesof the hydrosol prepared is not more than 1 micron. The time necessaryfor carrying out the polymerization in accordance with my invention isshort, the completion thereof being determined by the absence of theodor of any monomer in the reaction mass. The resulting dispersionobtained may be used directly in mixing with aqueous gelatincompositions or in any other connection in which use thereof isindicated. When the amide employed is acrylamide rather than asubstituted acrylamide, it is desirable to use the resulting productshortly after its preparation.

The examples presented herewith are intended to illustrate how ourinvention may be operated so as to improve the sizing of the sheet. Itis, of course, possible to size either (a) waterleaf paper or (b) paperwhich has already been beater sized. Examples of both processes andresults obtained are given below.

Example I .T ub sizing of waterleaf paper Percent n-Butyl acrylate 59.1Styrene 25.2 Methacrylamide 15.7

The hydrosol was diluted to a solid content of 4.4 percent.

agmahae 5 Twelve pound waterleaf paper was cut into:8:in. X: 1.0v in.size, hand dipped into the dilute size, and;theexcess: removed bypassing through two power drive press rolls; Thesheets were then driedat 220 F. for three minutes. on a rotary'drum dryer.

Physical tests were run on these sheets:

PHYSICAL PROPERTIES OF TUB-SIZED 12% LB. VVATERLEAF PAPER Example II.Tubsizing of already beater-sized paper The stock used for tub sizing thealready beater-sized paper was white Insurance R stock, previouslyuntubbed. This stock was treated with a hydrosol and gelatin mixturehaving 2.2% Gelatin and 2.2%. Hydrosol.

The'beater-sized stock was hand dipped into the dilute. size, and theexcess removed by passing'through, two. power drive press rolls. Thesheets were then dried at. 220 F. for three minutes on a rotary drumdryer;

The results of physical tests obtained upon the already beater-sizedpaper after tub sizing are given below.

PHYSICAL PROPERTIES OF PRODUCT F. TUB SIZING ALREADY BEATER-SIZEDBAPER2.27 Gela- Gelatin 0 4.47 Property tin, 2.2% 0

4.4%) Hydrosol (Check) Hydrosol Weight, 1b./l,000 It. 20 21 22Thickness: A Wet mils 5. 2 5.2 5. 2 Dry 111115 6. 8 6. 6f 6.3.7 Tear 6876 68 C 68 72 72 Mullen, lb./in. 34 34 33 Wet Strength, lb. 14 15%Penetration, sec. 135 135 213 Expansion, percent- 3. 02 2. 81 2. 91Tensile:

6P K 9/50 mm. width 7.8 7. 9 7. 8 C K9/50 mm.width 4.2 4.0 3. 9 WetTensile:

L K 9/50 mm. Width 2. 23 2. 15 2. 22 C K 9/50 mm. width 1. 34 1. 33 1.33Porosity, sec 112 39 28 Cobb Size, 5 min. Distilled H grams 0. 227 0.239 0. 169 Fold:

L 60 47 58 37 44 43 Permanence, percen 88 85 85 76 73 73 UV Reversion:

B "percent" 87. 9 87. 9 87. 1 R d 85.5 86.1 85.2 Difi d0 2. 4 1.8 1.9

Portions of the already beater-sized, subsequently tubsized samples,were directly sensitized with a photographic emulsion. These were testedsensitometrically and for general photographic quality, fresh and aftervarious incubation periods at 120 F. and percent relative humidity up to32 days. Results of these tests showed that, in general, no markedchanges have been brought about in the photographic characteristics ofthe emulsion, through the use of this hydrosol either as partial ortotal replacement for gelatin in the tub-sizing process.

gelatinrby the hydrosol has (a) improved the sizing (as.

measured" either by Valley Penetration or Cobb size), (b) greatlyincreased the porosity, and (0) left the rest of the properties,essentially unaltered. (Porosity as. usedin this sense means porosity ofthe dry sheet to air.)"

It should be understood that our invention should be more broadlyconstrued than to only include the particular hydrosol compositionmsedin the above examples. Any of the hydrosols described in application No.272,709 might easily be substituted for this one; the degree of sizingdepending to a considerable extent upon the relative amounts ofhydrophilic and..hydrophobic monomers used.

The Cobb size test is described in T. A. P. P. 1. Method T441m45.

Valley penetration test is described in T. A. P. P. I. Instrumentation,Study XVI,v Correlation Between the Degree of Sizing as Determined byValley, T. A. P. RI. and CurrierMethods.

We claim:

1. Aprocess for tub sizingphotographic paper wherein the paper is sizedby a hydrosol prepared by polymerizing.

R3 are selected from the group consisting of hydrogen and.

alkyl, a monomer. having the structural formula:

R4 CH'z= JQ-O-Ru wherein R4 isza substituent selected from the groupconsisting ofhydrogen, halogen and alkyl, and R5 is a substituentselected from the group consisting of alkyl, cyano.

alkyl and halogenated alkyl, and a monomer. havingthe formula:

Re i l-C H:

R R o wherein R6 is a substituent selected from the group consisting ofhydrogen, halogen and alkyl, and R7, R8, R9, R10 and R11 aresubstituents, each of which is selected from any of the following:hydrogen, halogen, alkyl, nitro, cyano and dialkyl amino, each of thefirst two monomers constituting at least 2% of the total monomerpresent, and their sum being at least 30% thereof, and the third monomerbeing no more than of the total monomer present and using the hydrosolas originally formed.

2. A process for tub sizing photographic paper wherein the paper issized with a hydrosol prepared by polymerizing in an aqueous system amixture of monomers having the following formula:

wherein R1 is a substituent selected from the group consisting ofhydrogen, halogen, alkyl and cyano, and R3 .7 and R3 are selected fromthe group consisting of hydrogen and alkyl, a monomer having thestructural formula:

wherein R4 is a substituent selected from the group consisting ofhydrogen, halogen and alkyl, and R5 is a substituent selected from thegroup consisting of alkyl, cyano alkyl and halogenated alkyl, and amonomer having the formula:

wherein R6 is a substituent selected from the group consisting ofhydrogen, halogen and alkyl, and R1, R8, R9, R10 and R11 aresubstituents, each of which is selected from any of the following:hydrogen, halogen, alkyl, nitro, cyano and dialkyl amino, the first andsecond monomers each constituting at least 2% and their sum constituting3095% of the total monomer present, and the third monomer constituting70% of the total monomer present and using the hydrosol as originallyformed.

3. A process for sub sizing photographic paper wherein the paper issized with a hydrosol prepared by polymerizing 40 parts ofmethacrylamide, 5.04 parts of sodium lauryl sulfate and 1.26 parts ofpotassium persulfate in 1000 parts of hot water while heating thissolution, introducing thereto 150 parts of n-butyl acrylate and 64 partsof styrene, and continuing the heating of the mass until a white opaquehydrosol is obtained.

4. A process for sub sizing photographic paper wherein the paper issized with a hydrosol prepared by polymerizing together a mixture of thefollowing: 20 parts of N-isopropylacrylamide, 75 parts of n-butylacrylate, 32 parts of styrene, 500 parts of cold water, .127 part ofpotassium persulfate, .127 part of sodium acid sulfite and 2.5 parts ofsodium lauryl sulfate until no odor of monomer is present in the massand a white opaque hydrosol results.

5. A process for tub sizing photographic paper wherein the paper issized with a hydrosol prepared by polymerizing together with agitation1000 parts of hot water, 1 part of potassium persulfate, 5 parts ofsodium lauryl sulfate, 40 parts of methacrylamide, 77.5 parts ofpchlorostyrene and 136 parts of n-butyl acrylate, and supplying heat tothis mixture until a white opaque hydrosol results.

6. A paper containing as a sizing agent a hydrosol prepared bypolymerizing together in an aqueous solution of an unsaturated aliphaticamide, the mixture of the amide, an aliphatic acrylate and a styrenemonomer, the amide and the acrylate each constituting at least 2% of themonomer present, and their sum constituting at least 30% thereof, andthe styrene monomer constituting not more than of the total monomerpresent therein and using the hydrosol as originally formed.

7. A process of sizing paper comprising tub sizing the paper with ahydrosol obtained by polymerizing n-butyl acrylate, styrene andmethacrylamide in an aqueous system and using the hydrosol as originallyformed.

8. A process for sizing photographic paper comprising tub sizing thepaper with a hydrosol formed by polymerizing together in an aqueoussolution of an unsaturated aliphatic amide, a mixture of the amide, analiphatic acrylate and a styrene monomer, the amide and the acrylateeachconstituting at least 2% of the monomer present, and their sumconstituting at least 30% thereof and using the hydrosol as originallyformed.

9. A process for tub sizing photographic paper wherein the paper issized with a hydrosol prepared by polymerizing in an aqueous systemmethacrylamide, n-butyl acrylate and styrene, the methacrylamide andn-butyl acrylate constituting at least 2% and their sum at least 30% ofthe total monomer present and using the hydrosol as originally formed.

References Cited in the file of this patent UNITED STATES PATENTS2,123,599 Fikentscher July 12, 1938 2,140,048 Fikentscher Dec. 13, 19382,343,095 Smith Feb. 29, 1944 2,550,652 Dreschel Apr. 24, 1951 2,592,218Weisgerber Apr. 8, 1952 OTHER REFERENCES Serial No. 397,138, Fikentscher(A. P. C.), published May 9, 1943.

1. A PROCESS FOR TUB SIZING PHOTOGRAPHIC PAPER WHEREIN THE PAPER ISSIZED BY HYDROSOL PREPARED BY POLYMERIZING TOGETHER IN AN AQUEOUS SYSTEMAND UNSATURATED ALIPHATIC AMIDE HAVING THE FOLLOWING STRUCTURAL FORMULA: